1. Field of Invention
Clear reddish water-soluble norbixin adducts with improved tinctorial power and stability in light and under acidic conditions.
2. Background of the Invention
This specification describes a new and novel adduct form of norbixin, a dicarboxylic acid carotenoid derived from annatto seed.
This seed is produced by a tropical bush, indigenous to the Amazon basin and presently cultivated in the tropics throughout the world. The outside of the seed is covered with as much as 1% to 2% bixin, which is the monomethyl ester of norbixin. The bixin is readily removed from the fresh seeds as a paste, and as such is used as a cosmetic and food color by the peoples indigenous to the Amazon area. Since settlement of the New World, it has become a common colorant for fats, in its paste form, and more recently has been refined and prepared as a microcrystalline suspension in vegetable oil or as a more dilute solution in vegetable oil. These forms of bixin are used to color margarine, butter, frying oils and, when dispersed on carriers such as salt, as seasonings for sauces and the like. Preparations comprising bixin are now generally made by solvent extraction and purification of the pigment.
Norbixin, being saponified bixin, is made by the alkaline saponification of bixin. This is most commonly done by extracting the seeds with aqueous alkali and heating. The resulting product, known commercially as "cheese color", is the basis of the coloring of most cheddar cheeses. It is added directly to the churn or milk, which is acid, and which precipitates the norbixin, which in turn colors the butterfat during fermentation. This direct alkaline extract contains other alkali-soluble materials, many of which are brownish in shade, and these also contribute to the coloration of the cheese. This tends to reduce the chroma, which is the equivalent of introducing more gray into the pigment. For applications which require a higher chroma, norbixin is made by saponification of relatively pure bixin, which has been prepared by crystallization from a solvent such as ethyl acetate or chloroform. This improves the chroma, and therefore the brightness of the color. Such type of product may be used to give an orange cast to cereals, by addition of the alkaline norbixinate solution or powder to the dough, wherein norbixin precipitates due to the acidity. Upon cooking, it distributes the orange color throughout the batter.
Because norbixin made from pure bixin--75% pure or more--has greater chroma and purity of hue, it is the preferred form of norbixin for use in forming the adduct described in this specification. However, the less pure, conventional cheese color types may also be employed where purity of color is not of paramount significance.
Norbixin is insoluble in water, whereas the salts, such as potassium norbixinate (very soluble) and sodium norbixinate (less soluble), dissolve under alkaline conditions to give an orange color. These salts are available in dry as well as liquid form, either admixed with an alkaline earth carbonate carrier, or dried and mixed with a modified food starch. These dry products have the same properties as the aqueous norbixinate solutions, being dispersible in water, possessing an orange shade, and being useful for mixing into flours or seasoning. In addition, norbixin may be precipitated from its norbixinate solution by the addition of acid, and the resulting liquid dispersed on salt to give a product suggested for seasoning salt coloration.
The art also shows the preparation of a "lake" type water-insoluble coloring made by admixing norbixinate solution with cellulose, boiling, adding salt to "fix" the pigment on the cellulose, removing the water and excess norbixinate by filtration, and washing finally with very dilute acetic acid to provide a neutral powder. The color, while brownish, and not the orange of the conventional norbixinate preparations, is said to be suitable for coloring tablets. It is not suggested for use as a food coloring.
Additionally, norbixinate preparations are made using polysorbate 80 and optionally propylene glycol. The polysorbate 80 is a common food grade emulsifier and, upon addition to acidic media the norbixinate in solution in the polysorbate 80 changes to norbixin, which remains emulsified by the polysorbate 80. These solutions are orange, and their chroma and purity will depend upon the purity of the bixin used to make the norbixinate. They are called "acid-stable" annatto colors, and are useful in sauces and dressings.
An understanding of the adduct described in this specification is assisted by using the empirical formulas and molecular weights of the annatto carotenoids:
______________________________________ bixin: monomethyl ester, mono free carboxylic acid C.sub.25 H.sub.40 O.sub.4 MW 394 norbixin: dicarboxylic acid C.sub.24 H.sub.38 O.sub.4 MW 380 norbixinate alkaline salt of norbixin: potassium C.sub.24 H.sub.36 O.sub.4 K.sub.2 MW 456 sodium C.sub.24 H.sub.36 O.sub.4 Na.sub.2 MW 424 ______________________________________
As described above, the norbixinates become free norbixin upon addition to foodstuffs, which are acidic, and wherein they express their expected orange to orange-brown color.